**2.2 Zibaishan ice cave**

Zibaishan ice cave (33.7°N, 106.68°E; 2450 m asl) was found in August 2015, and it is located in the shaded slope of Zibai Mountain, Liuba County, Shanxi Province. Fieldwork was conducted in May 2016, and then the geometry and temperature profile of the ice cave was measured. The measurements are shown in **Figure 2a**. The cave space has a depth of about 90 m. The widest part is at the bottom with a width above 25 m.

Zibaishan ice cave, located in Zibaishan National Forest Park, is also a major tourist attraction. Most of the tourists only visited the opening of the ice cave, and a few experienced adventurers with professional climbing equipment could reach the interior of the ice cave. Consequently, Zibaishan ice cave maintained better natural environments (because of little artificial effects) than Ningwu ice cave. Ice deposits of the ice cave mainly included two parts: (1) ice cone which has a diameter of 25 m and a height of 16 m (**Figure 2b**) and (2) ice stalactites (**Figure 2c**). Ice deposits covered wall rocks of the ice cave partially. The host rock consists of limestone.

The outside of Zibaishan ice cave belongs to the warm temperate zone and humid monsoon section. The external annual mean air temperature is 11.5°C, and the frost-free period is 214 days per year [23]. Generally, ice deposits could not be preserved under such a temperate environment. Therefore, there must be some special cooling mechanisms of Zibaishan ice cave.
